The InnoDB internal SQL parser, which is used for updating the InnoDB data dictionary tables (to be removed in MDEV-11655), persistent statistics (to be refactored in MDEV-15020) and fulltext indexes, implements some unused keywords:

OUT BINARY BLOB INTEGER FLOAT SUM DISTINCT READ COMPACT BLOCK_SIZE TO_CHAR TO_NUMBER BINARY_TO_NUMBER REPLSTR SYSDATE PRINTF ASSERT RND RND_STR ROW_PRINTF UNSIGNED

Also, procedures are never declared with parameters. For passing parameters to procedures, a separate interface (pars_info_t) is being used.